Aeroplane-propeller.



C. A. CUTLER.

AEROPLANE PROPELLER. APPLICATION FILED AUG.3I; 191s.

Patented Apr. 22,1919.

wag

1N ZVTOB A T'TOENEY cnrroan A. CUTLER, or BurrALo, new voax.

AJEBOPLANE-PROPELLER.

Specification of Letters Patent.

Patented Apr. 22,1919.

Application filed August 81, 1916. Serial No. 117,849.

To all whom it may concern:

Be it known that I, CLIFFORD A. CUTLER, a citizen of the United Statesof America, residing at Buffalo, in the county of Erie and State of NewYork, have invented certain new and useful Improvements inAeroplane-Propellers, of whlch the following is a full, clear, and exactdescription.

It is well known to those skilled in the art, that aeroplane propellersof the present art are formed out of a block of wood made of five ormore pieces of material, ofttimes of different kinds, glued together.The result of this construction is that each of the blades of thefinished propeller comprises' everal different pieces of material. It iswell known that no two pieces of material have exactly the samecoeflicient ofexpansion. Therefore, there is always a strain set upbetween the laminae by reason of different climatic or temperatureconditions. When a blade of this type is put under load the laminae aresubjected to additional strain and this tension added to the tensionexisting in the section ofttimes results in the rupture and breaking ofthe blades. Furthermore, blades of the present art are usually made withthe wide portion or working surface of the blade near the tip.

In my invention I have sought to. overcome the disadvantages aboveenumerated and to provide a propeller formed with single piece blades,thereby eliminating all undue strain.

My propeller is so designed that the surface receiving the eatest loadcomes near the reinforced hub instead of at the tip as is usualpractice, and therefore I very strong propeller.

Furthermore, I havesought to provide a propeller in which the bladesshall. have a true pitch throughout their length.

Moreover, the blades of my propeller are so designed that they arenarrower at their tips than near the hub and are thus flexible so thatthey will yield and thereby drop part of an excessive load.

I The above objects and advantages have been accomplished by the deviceshown in the accompanying drawings, in which:

Figure 1 is an elevation showing the front or advance side of thepropeller.

Fig. 2 is an elevation showing the rear or trailing side ofthepropeller.

F 3 is a side elevation of the propeller.

Fig. 4 i a perspective view showing the provide a pro eller in the roughand before it is wor ed u to shape.

Fig. 5 1s a sectional view taken on line 5-5 of Fig. 4.

Fig. 6 is an enlarged sectional view of the propeller taken on line 6-6of Fig. 1.

Fig. 7 is an enlarged sectional view of the propeller taken on line 7--7of Fig. 1.

Fig. 8 is an enlarged sectional view of the propeller taken on line 88of Fig. 1.

Fig. 9 is an enlarged sectional View of the propeller taken on llne 99of Fig. 1.

Fig. 10 is an enlarged sectional view of the pro eller takenon line10-10 of Fig. 1.

y propeller is formed essentially of three parts, namely, a center hubblock 11 and two blades 12. The hub part 11 is of laminated constructionand formed of a number of pieces of plain sawed wood 13, glued togetherin the usual manner. block is finished and the glue is set, there is cutinto each end thereof a slot 14. These slots are cut diagonally acrosseach end of the block and in opposite directions and terminated at thecenter. The outer boundary of the slot is coincident with the corner ofthe block as clearly shown in Figs. 4 and 5. The inner end of each slot,at the center of the block, forms an acute angle 17 with the innersurface of the slot as clearly shown in Figs. 1 and 3. In each of, theseslots is placed one of the blades 12.

The blades 12of my propeller are preferably made of quarter sawed oakand the two blades are preferably made from the same board. This boardis sawed at the middle and the ends 15 are then reversed,

so that they will form the tips of the blades. By this construction I ammore certain of getting material in the tips of the blades which is moreuniform in texture and weight. The ends 16 of the boards which are to beplaced in the block 11 are chamfered atan angle which will fit the angle17 formed at the bottom of the slot 14:. After these boards forming theblades 12 are fitted to their respective slots, they are glued inposition and when dry the pro peller is then ready to be finished.

. The proportions of the center hub block, 11 are such that when theslot 14 is formed diagonally therein, the angle of such slot will besubstantially the general angle formed by the finished blade. By thisconstruction it will be seen that the major part of the blade 12 will beformed from a sin- After this gle piece of material. Inasmuch as theblades 12 are made from quarter sawed material, preferably oak, it willbe clear that the flights of the material will run parallel with theface of the blade, thus reducing the tendency to warp to a minimum. Itis well known that quarter sawed wood does not weather check and that itshrinks and swells in thickness only and not in width, thereby producingapropeller blade which keeps its shape, without internalstrains, undervarying atmospheric conditions.

By reason of my improved construction, I am enabled to provide theWidest area of the blade near the hub, and from the drawings it will benoticed that the working area of the blade starts at substantially thevertical center line. By this construction the efficient work done bythe propeller is kept near the hub where the necessary amount ofstrength can be provided. This also permits the blade to be tapered offand made thin and flexible at its outer end, whereby when my propellerstrikes an overload the tips of the blades may flex or bend somewhat andthus automatically drop a part of the load and relieve the strain on thepropeller. The line of work in my propeller is nearly radial andtherefore the centrifugal force does not tend to distort the blade, buttends to stiffen it.

18 are the hub plates of the propeller, which, as usual, are secured tothe propeller by a plurality of bolts 19 passing through the material ofthe propeller, from one late to the opposite plate. As the boards ormingthe blades 12 eachterminate at the center of the hub, it is clear thatsubstantially all of these bolts 19 pass through the boards thus firmlysecuring them in place against centrifugal force.

As the efficiency of any blade depends upon its width andspeed, I haveformed my blade with its Widest part at the hub and its narrowest partat the tip. In this way the greater width at the hub makes up for theslower speed at this point and thereby also reduces the resistance ofthe rotary motion.

Obviously some modifications of the details herein shown and describedmay be made without departing from the spirit of posite directionsbetween the corners to the center of the hub block where the inner endsof the slots terminate across each other and end blades fitted into andoccupying the whole width of the slots.

In testimony whereof, I have hereunto signed my name in the presence oftwo subscribing witnesses.

I CLIFFORD A. CUTLER.

Witnesses:

J. WM. ELLIS, WALTER H. KELLEY.

